Hi Markus and others:
Apologies for my delay in responding to the questions raised in this thread. Many thanks everyone for the considered input on the issue.
With regard to Markus' various questions about whether to create a globally unique system of GBIF identifiers for taxa, I started trying to give answers based on how I hope to interact with the GBIF system and found myself having to review many parts of this thread to give a considered answer. Perhaps the best response I can give is to explain how I depend on taxon identifiers in external systems.
My system includes documentation of a set of taxa. That documentation references external sources, including resources like WoRMS, ITIS, and Atlas of Living Australia. I need to:
1. Know that the external sources are all describing the taxon documented by my system. 2. Know how to ask the web service exposed by each external source for updated information about the taxon including what name that external source deems to be valid for the taxon.
Currently my system starts with a kingdom, a taxonomic rank and a name for a taxon (ideally that would also include a reference to a paper but it does not for now) and uses that information to test whether there is a matching taxon in each external system. If I get a match I can be fairly confident that I have found a new external source pertinent to the taxon in my system. Each taxon in my system has a bunch of identifiers, a local one, that happens to have an LSID syntax, and external ones that are either LSIDs or IDs local to external systems that have been made global by adding a prefix to create a globally unique identifier with a LSID syntax.
My system regularly reviews the external identifiers associated with each locally documented taxon to determine if they identify a taxon with a valid name, and the same name/rank as the locally documented taxon. External identifiers indicated to be associated with invalid names are replaced. When external services indicate that a replacement is not possible, because the taxon has been marked as obsolete, then my system is update to reflect that change (somewhat more manually).
I hope that perspective is useful,
Regards
Geoff Shuetrim